JP2009-235717A discloses a control system for hybrid construction machine.
In this conventional control system, oil discharged from a variable-capacity sub-pump is joined at a discharge side of a variable-capacity main pump and the sub-pump is driven by an electric motor. A tilting angle of the main pump is controlled by the action of a pilot pressure generated according to an operated amount of a control valve.
An assist force of the sub-pump for the main pump is set beforehand so as to be most efficient in response to the pilot pressure.